WO2018181080A1 - Glitter ink-jet ink and method for forming image using same - Google Patents

Abstract

A glitter ink-jet ink which comprises metal nanoparticles, a dispersant adsorbed onto the surface of the metal nanoparticles, emulsion resin particles, and a solvent and which satisfies 0.05<D2/D1<1 where D1 is the average particle diameter of the metal nanoparticles and D2 is the average particle diameter of the emulsion resin particles.

Description

Glossy inkjet ink and image forming method using the same

The present invention relates to a glittering inkjet ink and an image forming method using the same.

Conventionally, an ink containing a metallic pigment-based glitter pigment such as an aluminum pigment or a pearl pigment is used to form an image that emits a metallic luster color in a record such as a label, a package, an advertisement printed matter, or a photograph. is there. These images are formed by analog printing such as offset printing, gravure printing, and screen printing.

In recent years, with the development of digital printing, a method for forming an image that emits a metallic glossy color by an ink jet method has been studied. As an ink used for forming such an image, Patent Document 1 discloses an ink composition for ink jet printing including silver nanoparticles, a specific organic compound and a polymer dispersant that coats the silver nanoparticles, and a solvent. Things are disclosed. Patent Document 2 discloses a glitter pigment ink containing silver nanoparticles (a glitter pigment), a urethane resin, and water.

JP 2009-227736 A Japanese Patent Laying-Open No. 2015-193721

However, since the ink of Patent Document 1 does not contain a binder resin, it is difficult to obtain an image having sufficient adhesion to a substrate, particularly a non-absorbent substrate. On the other hand, although the ink of patent document 2 contains urethane resin (binder resin), sufficient metal luster was not obtained.

The present invention has been made in view of such circumstances, and an object of the present invention is to provide an ink-jet ink that can form an image having sufficient adhesion to a substrate and having sufficient metallic luster. .

[1] A metal nanoparticle, a dispersant adsorbed on the surface of the metal nanoparticle, an emulsion resin particle, and a solvent, wherein the average particle diameter of the metal nanoparticle is D1, and the average particle diameter of the emulsion resin particle A glittering inkjet ink satisfying 0.05 <D2 / D1 <1, where D is D2.
[2] When the content mass of the metal nanoparticles is M1 (%) and the content mass of the emulsion resin particles is M2 (%), 1.3 ≦ M1 / M2 ≦ 35 is further satisfied. Glitter ink jet ink.
[3] When the content mass of the metal nanoparticles is M1 (%) and the content mass of the emulsion resin particles is M2 (%), 1 ≦ M1 + M2 ≦ 35 is further satisfied, [1] or [2] Glitter ink jet ink.
[4] The glittering ink-jet ink according to any one of [1] to [3], wherein the dispersant is a polymer dispersant.
[5] The glitter according to [4], wherein the dispersant is a comb block copolymer in which a main chain includes a structural unit derived from a (meth) acrylic acid ester and a side chain includes a polyoxyalkyl group. Inkjet ink.
[6] The glittering inkjet ink according to any one of [1] to [5], wherein the emulsion resin particles are urethane resin particles or (meth) acrylic resin particles.
[7] The glittering ink-jet ink according to any one of [1] to [6], wherein the solvent includes an organic solvent having a boiling point of 150 ° C. or higher.
[8] The glittering ink-jet ink according to any one of [1] to [7], wherein the metal nanoparticles are silver nanoparticles.
[9] After applying the glittering inkjet ink according to any one of [1] to [8] on the substrate, the step of volatilizing the solvent, and heating the glittering inkjet ink from which the solvent has been volatilized are heated. And forming a metallic gloss layer.

The present invention can provide an ink-jet ink that can form an image having sufficient adhesion to a substrate and sufficient metallic luster.

As described above, with the ink of Patent Document 2, a metallic luster layer having a sufficient metallic luster could not be obtained. The reason is presumed as follows. In the ink of Patent Document 2, the average particle diameter of the emulsion resin particles is relatively larger than the average particle diameter of the metal nanoparticles. Therefore, in the resulting metallic gloss layer, a thick resin layer is likely to be formed around the metal nanoparticles, resulting in light absorption and a low content ratio of the metal nanoparticles. Is likely to be lowered, that is, the metallic luster is likely to be impaired.

In Patent Document 2, in order not to impair the metallic luster, it is conceivable to reduce the resin component in the metallic luster layer, that is, to reduce the content of emulsion resin particles in the ink. However, just by reducing the content of emulsion resin particles having a relatively large average particle size, the gap between the emulsion resin particles existing around the metal nanoparticles tends to be large in the ink, and the resulting metallic gloss layer In many cases, many voids are easily formed around the metal nanoparticles. As a result, the refractive index of the resulting metallic luster layer tends to increase and the extinction coefficient tends to decrease. In addition, scattered light tends to increase. As a result, it is considered that the reflectance of the metallic luster layer tends to decrease (that is, it is difficult to obtain metallic luster).

On the other hand, the present inventors make the average particle diameter D2 of the emulsion resin particles relatively smaller than the average particle diameter D1 of the metal nanoparticle silver; specifically, the average particle diameter of the metal nanoparticles. By making the ratio D2 / D1 of D1 and the average particle diameter D2 of the emulsion resin particles less than 1, it has a high reflectance (that is, has a sufficient metallic luster) and has good adhesion to the substrate. It was found that a metallic luster layer having

That is, when D2 / D1 is less than 1, the average particle diameter D2 of the emulsion resin particles is relatively smaller than the average particle diameter D1 of the metal nanoparticles, so that the content of the emulsion resin particles in the ink is reduced. Even so, the surface of the metal nanoparticles can be covered relatively densely (with no relatively gaps) in the ink. Thereby, since the space | gap around a metal nanoparticle can be decreased in the obtained metallic luster layer, the increase in the refractive index of an metallic luster layer and the fall of an extinction coefficient can be decreased. Moreover, scattered light can be reduced. As a result, the reflectance of the metallic luster layer can be increased and the metallic luster can be easily obtained. Moreover, since the space | gap around a metal nanoparticle can be decreased in a metallic luster layer, adhesiveness with a base material and film | membrane intensity | strength can also be improved. On the other hand, if D2 / D1 is more than 0.05, the emulsion resin particles have an appropriate size, so that the emulsion resin particles are easily bonded to each other, and the adhesion to the substrate and high film strength are high. Easy to obtain. The present invention has been made based on such findings.

1. Glossy Inkjet Ink The glittering inkjet ink of the present invention includes metal nanoparticles, a dispersant adsorbed on the surface of the metal nanoparticles, emulsion resin particles, and a solvent.

1-1. Metal nanoparticles Metal nanoparticles are nano-sized metal particles. Examples of the main component of the metal nanoparticles include silver, gold, copper, aluminum, platinum, nickel, chromium, tin, zinc, indium, titanium, and bismuth. These metals may be alloys, mixtures or oxides containing the aforementioned metals. A main component means that it is 50 atomic% or more with respect to the sum total of all the atoms which comprise a metal nanoparticle, for example. Among these metals, gold, silver, and aluminum are more preferable from the viewpoint of high glossiness and manufacturability, and silver is more preferable from the viewpoint of stability and color. That is, the metal nanoparticles are preferably silver nanoparticles mainly composed of silver.

Examples of alloys containing silver include silver magnesium, silver copper, silver palladium, silver palladium copper, silver indium, and silver bismuth. Furthermore, the metal nanoparticles may contain a small amount of other components inevitably contained, and may contain a silver oxide. Commercially available products may be used for the metal nanoparticles.

The metal nanoparticles may be further surface-treated with citric acid or the like in order to improve dispersion stability. Moreover, the metal nanoparticle contained in an ink may be one type, and may be used combining two or more types from which a kind or composition differs.

The average particle diameter D1 of the metal nanoparticles is not particularly limited as long as D2 / D1 satisfies the range described later. However, the dispersion stability in the ink for forming the metallic gloss layer and the reflectance of the metallic gloss layer are not limited. From the viewpoint of obtaining smoothness sufficient to increase the thickness, it is preferably 3 nm or more and 200 nm or less, and more preferably 15 nm or more and 150 nm or less.

The average particle diameter D1 of the metal nanoparticles can be measured by SEM observation. Specifically, it can be measured by the following procedure.
1) SEM observation is performed in a state where the ink is applied to the glass substrate and the solvent component is volatilized by vacuum degassing without heating, or cryo SEM observation is performed in a state where the ink containing the solvent is frozen. In cryo SEM observation, the fractured surface of frozen ink is observed. And the particle diameter of arbitrary 300 metal nanoparticles is measured.
2) A volume-based particle size distribution is obtained based on the obtained measurement data, and the D50 (median diameter) is defined as the average particle diameter D1 (volume average particle diameter) of the metal nanoparticles.

In addition, the average particle diameter D1 of the metal nanoparticles in the present invention means the average particle diameter of the metal nanoparticles themselves that do not contain a dispersant (adsorbed on the surface of the metal nanoparticles).

The average particle diameter D1 of the metal nanoparticles can be adjusted by, for example, the dropping time of the reducing agent when preparing the metal nanoparticle dispersion described later.

1-2. Dispersant The dispersant is adsorbed on the surface of the metal nanoparticles. As a result, the metal nanoparticles are easily dispersed in the solvent, and the dispersion agent and the emulsion resin particles interact to facilitate uniform mixing of the metal nanoparticles and the emulsion resin particles via the dispersant. be able to. The dispersant is preferably a polymer dispersant from the viewpoint of excellent affinity with the emulsion resin.

The polymer dispersant is a resin having an adsorbing group for adsorbing on the surface of the metal nanoparticles. Examples of the adsorbing group include a carboxyl group and a thiol group. That is, in the present invention, whether or not the dispersant is adsorbed on the surface of the metal nanoparticles is determined by whether or not the dispersant has an adsorbing group and the metal nanoparticles are less aggregated and well dispersed. be able to.

The resin constituting the polymer dispersant is preferably a hydrophilic monomer alone or a copolymer. The copolymer of hydrophilic monomers may be a copolymer of hydrophilic monomers and hydrophobic monomers.

Examples of hydrophilic monomers include carboxyl group or acid anhydride group-containing monomers ((meth) acrylic acid such as acrylic acid and methacrylic acid, unsaturated polycarboxylic acid such as maleic acid, maleic anhydride, etc.), alkylene Oxide modified (meth) acrylic acid ester monomers (such as ethylene oxide modified (meth) acrylic acid alkyl ester) and the like are included.

Examples of hydrophobic monomers include (meth) acrylic acid ester monomers such as methyl (meth) acrylate and ethyl (meth) acrylate; styrene monomers such as styrene, α-methylstyrene and vinyltoluene; ethylene, propylene And α-olefin monomers such as 1-butene; vinyl carboxylic acid ester monomers such as vinyl acetate and vinyl butyrate, and the like.

When the polymer dispersant is a copolymer, it may be any of a random copolymer, an alternating copolymer, a block copolymer, or a comb copolymer (or a comb graft copolymer). Among them, the polymer dispersant is preferably a comb block copolymer from the viewpoint of good affinity with emulsion resin particles described later.

The comb block copolymer refers to a copolymer including a linear polymer that forms a main chain and another type of polymer that is graft-polymerized to a structural unit derived from a monomer that forms the main chain. Preferable examples of the comb block copolymer include a main chain containing a structural unit derived from (meth) acrylic acid ester and a side chain containing a polyoxyalkyl group (such as a long-chain polyoxyalkyl group such as an EO-PO copolymer group). Comb type block copolymers containing a group) are included. In the comb-type block copolymer, since the graft-polymerized side chain causes steric hindrance, aggregation of metal nanoparticles can be further suppressed. Thereby, the dispersibility of the metal nanoparticles is increased, and thus it is easier to suppress ejection failure due to the aggregated metal nanoparticles.

The acid value of the dispersing agent is preferably 1 mgKOH / g or more and 80 mgKOH / g or less. When the acid value is 1 mgKOH / g or more, the dispersant has a tendency to be hydrophilic, and therefore, the dispersibility in the ink (particularly the water-based ink) is easily improved. When the acid value is 80 mgKOH / g or less, it is easy to suppress a significant decrease in durability of the metallic gloss layer due to swelling of the dispersant in the metallic gloss layer. The acid value of the dispersant is more preferably 1 mgKOH / g or more and 50 mgKOH / g or less, further preferably 2 mgKOH / g or more and 40 mgKOH / g or less, further preferably 3 mgKOH / g or more and 30 mgKOH / g or less. It is preferably 5 mgKOH / g or more and 20 mgKOH / g or less.

The acid value can be measured according to JIS K 0070. Specifically, the acid value of the dispersant is identified by the type of the dispersant (for example, the product name of the polymer dispersant used for image formation) by Fourier transform infrared spectroscopy (FT-IR). The acid value of the same dispersant may be measured according to JIS K 0070. Further, the type of the dispersant may be specified by ¹ HNMR or gas chromatography-mass spectrometry (GC / MS).

The molecular weight of the dispersant is preferably 1000 or more and 100,000 or less, and more preferably 2000 or more and 50000 or less.

Examples of commercially available dispersants include Solsperse 24000, Solsperse 24000GR, Solsperse 32000, Solsperse 44000, Solsperse 46000 (manufactured by Lubrizol Corp.); DISPERBYK-187, DISPERBYK-194N, DISPERBYK-190, DISPERBYK-191, DISPERBYK-199, DISPERBYK-2000, DISPERBYK-2001, DISPERBYK-2015, DISPERBYK-2050, DISPERBYK-2B, and DISPERBYK-2B , "DISPERBYK" Disparon ED-152, ED-211, ED-212, ED-213, ED-214, ED-251 (Enomoto Kasei), PLAAD series (Enomoto Kasei); EFKA 6220 (BASF) "EFKA" is a registered trademark of the company), and Floren TG-750W (manufactured by Kyoeisha Chemical Co., Ltd.).

The dispersant adsorbed on the surface of the metal nanoparticles can be obtained, for example, by reducing silver ions (which become metal nanoparticles) in an aqueous solvent containing the dispersant.

1-3. Emulsion resin particles The emulsion resin particles can function as a binder resin, and can interact with the dispersant adsorbed on the surface of the metal nanoparticles to enhance the adhesion of the metal nanoparticles to the substrate. Such an emulsion resin particle is preferably a resin having a high affinity with a dispersant. Examples thereof include (meth) acrylic resin, urethane resin, polyolefin resin, polyester resin, and polyvinyl chloride resin (for example, Polyvinyl chloride polymer, vinyl chloride-vinylidene chloride copolymer), epoxy resin, polysiloxane resin, fluororesin, styrene copolymer (for example, styrene-butadiene copolymer, styrene- (meth) acrylic acid ester copolymer) Etc.), vinyl acetate copolymers (for example, ethylene-vinyl acetate copolymers, etc.) and the like. Above all, from the viewpoint of improving the water resistance of the obtained metallic luster layer, (meth) acrylic resin, urethane resin, polyolefin resin, polyvinyl chloride resin, epoxy resin, polysiloxane resin, fluororesin, styrene copolymer, vinyl acetate A copolymer is preferable, and a urethane resin or a (meth) acrylic resin is more preferable.

For example, the urethane resin can be reacted after the sulfonate-containing polyol (a1) and the organic polyisocyanate (a2) are reacted in an isocyanate group-excess atmosphere; the low-molecular polyol (a3-1) and an aqueous solvent are added. To obtain an emulsion of an isocyanate group-terminated prepolymer; a low molecular polyamine (a3-2) may be added and further reacted.

Examples of the sulfonate-containing polyol (a1) include a sulfonate-containing polyester polyol, a sulfonate-containing polyether polyol, a sulfonate-containing polycarbonate polyol, and the like.

Examples of the organic polyisocyanate (a2) include aromatic diisocyanates such as 4,4′-diphenylmethane diisocyanate, aliphatic diisocyanates such as 1,6-hexamethylene diisocyanate and 1,4-tetramethylene diisocyanate, o-xylene diisocyanate, Included are alicyclic diisocyanates such as m-xylene diisocyanate and p-xylene diisocyanate, and alicyclic polyisocyanates such as isophorone diisocyanate (hereinafter abbreviated as IPDI).

The low molecular polyol (a3-1) and the low molecular polyamine (a3-2) can function as a chain extender. Examples of the low molecular polyol (a3-1) include ethylene glycol, 1,2-propanediol, 1,3-propanediol, 1,4-butanediol, etc .; low molecular polyamine (a3-2) Examples include ethylenediamine, propylenediamine, diethylenetriamine and the like.

The aqueous solvent may be a mixed solvent of an organic solvent such as N-methylpyrrolidone (NMP) or propylene glycol dimethyl ether (DMPDG) and water.

The (meth) acrylic resin may be obtained by polymerizing the monomer (b1) using the water-soluble initiator (b2) in an aqueous solution containing the polymer emulsifier (b3).

Examples of the monomer (b1) include (meth) acrylic acid alkyl esters such as methyl (meth) acrylate and ethyl (meth) acrylate; (meth) acrylic acid alkoxyalkyl esters such as methoxybutyl (meth) acrylate; styrene, α -Aromatic vinyl compounds such as methylstyrene; hydrolyzable silane group-containing vinyl compounds such as vinyltriethoxysilane; (meth) acrylamide compounds such as N-methylolacrylamide and the like.

Examples of the water-soluble initiator (b2) include sodium persulfate, potassium persulfate, ammonium persulfate and the like.

The polymer emulsifier (b3) may be a water-soluble resin, and examples thereof include a carboxyl group-containing polymer. The carboxyl group-containing polymer is a homopolymer or a copolymer of a carboxy group-containing unsaturated monomer. Examples of carboxy group-containing unsaturated monomers include (meth) acrylic acid; examples of monomers copolymerizable therewith include those similar to monomer (b).

The ratio D2 / D1 between the average particle diameter D1 of the metal nanoparticles and the average particle diameter D2 of the emulsion resin particles preferably satisfies 0.05 <D2 / D1 <1. When D2 / D1 is less than 1, the surface of the metal nanoparticles can be covered with the emulsion resin particles relatively densely (with no relatively gaps) in the ink even if the emulsion resin particle content is small. Even in the metallic luster layer, voids around the metal nanoparticles can be reduced. Thereby, an increase in the refractive index and a decrease in the extinction coefficient of the metallic gloss layer can be reduced, and the scattered light can also be reduced, so that the reflectance (glossiness) can be increased. Moreover, since the space | gap around the metal nanoparticle in a metallic luster layer can be decreased, adhesiveness with a base material and film | membrane intensity | strength can also be improved. On the other hand, when D2 / D1 exceeds 0.05, the emulsion resin particles are easily bound to each other, so that high adhesion to the substrate and high film strength are easily obtained. The ratio D2 / D1 more preferably satisfies 0.1 <D2 / D1 <1, and more preferably satisfies 0.2 <D2 / D1 <0.95.

The average particle diameter D2 of the emulsion resin particles can be measured in the same manner as the method for measuring the average particle diameter D1 of the metal nanoparticles.

When the emulsion resin particles are urethane resin particles, the average particle diameter D2 is determined based on the addition amount of the chain extender (a3) and the reaction product of the sulfonate-containing polyol (a1) and the organic polyisocyanate (a2). It can be adjusted by the reaction time with the chain extender (a3), the composition of the aqueous solvent (such as the content ratio of DMPDG), and the like. When the emulsion resin particles are (meth) acrylic resin particles, the average particle diameter D2 is, for example, the composition of the monomer (b1) (styrene content ratio, etc.), the blending amount of the water-soluble initiator (b2), the polymer emulsifier ( It can be adjusted by the composition of b3).

By making D2 / D1 below a certain level, as described above, even if the contained mass M2 (%) of the emulsion resin particles is reduced, the periphery of the metal nanoparticles in the ink is relatively dense with the emulsion resin particles. Can be covered (with relatively no gap). That is, since the content mass M2 (%) of the emulsion resin particles in the ink can be reduced, the content ratio of the metal nanoparticles in the obtained metallic gloss layer can be increased, and thereby the reflectance can be increased. .

Specifically, the ratio M1 / M2 between the content M1 (%) of the metal nanoparticles in the ink and the content M2 (%) of the emulsion resin particles in the ink satisfies 1.3 ≦ M1 / M2 ≦ 35. It is preferable to satisfy. When M1 / M2 is 1.3 or more, the content ratio of the resin that easily absorbs light in the obtained metallic gloss layer can be appropriately reduced, and the content ratio of the metal nanoparticles can be appropriately increased. Easy to increase reflectivity. When M1 / M2 is 35 or less, since the content ratio of the resin in the obtained metallic luster layer is moderately high, it is easier to improve the adhesion and film strength of the metallic luster layer to the substrate. The ratio M1 / M2 more preferably satisfies 1.5 ≦ M1 / M2 ≦ 35, and more preferably satisfies 2 ≦ M1 / M2 ≦ 30.

When the above-mentioned ratio M1 / M2 of the contained mass is converted into a volume based on the specific gravity, the ratio V1 between the contained volume V1 (%) of the metal nanoparticles in the ink and the contained volume V2 (%) of the emulsion resin particles in the ink. / V2 preferably satisfies 0.25 ≦ V1 / V2 ≦ 6. When V1 / V2 is 0.25 or more, the content ratio of the resin that easily absorbs light in the obtained metallic gloss layer can be appropriately reduced, and the content ratio of the metal nanoparticles can be appropriately increased. Easy to increase reflectivity. When V1 / V2 is 6 or less, the content ratio of the resin in the obtained metallic luster layer is moderately high, so that the adhesion of the metallic luster layer to the base material and the film strength can be easily increased. V1 / V2 more preferably satisfies 0.4 ≦ V1 / V2 ≦ 5, and more preferably satisfies 0.6 ≦ V1 / V2 ≦ 4.

The total amount (M1 + M2) (%) of the contained mass M1 (%) of the metal nanoparticles in the ink and the contained mass M2 (%) of the emulsion resin particles in the ink preferably satisfies 1 ≦ M1 + M2 ≦ 35. If the total amount (M1 + M2) is 1 or more, the amount of solid content contained in the ink is moderately large, so that a metallic gloss layer having a desired thickness can be easily formed, and sufficient reflectance can be easily obtained. When the total amount (M1 + M2) is 35 or less, the amount of solids contained in the ink is not too large, so that the viscosity does not increase too much and the ejectability from the inkjet head is difficult to be impaired. The total (M1 + M2) preferably satisfies 2 ≦ M1 + M2 ≦ 35, and more preferably satisfies 3 ≦ M1 + M2 ≦ 30.

1-4. Solvent The solvent contains at least water, but may further contain an organic solvent in an arbitrary ratio.

Examples of organic solvents include ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol monobutyl ether, triethylene glycol monomethyl ether, triethylene glycol monoethyl ether, triethylene glycol Ethylene glycol monobutyl ether, tetraethylene glycol monomethyl ether, tetraethylene glycol monoethyl ether, tetraethylene glycol monopropyl ether, tetraethylene glycol monobutyl ether, propylene glycol monomethyl ether, propylene glycol monoethyl ether, propylene glycol monobutyl ether Glycol ethers such as ether, dipropylene glycol monomethyl ether, dipropylene glycol monoethyl ether, dipropylene glycol monopropyl ether; ethylene glycol, glycerin, 2-ethyl-2- (hydroxymethyl) -1,3-propanediol, Tetraethylene glycol, triethylene glycol, tripropylene glycol, 1,2,4-butanetriol, diethylene glycol, propylene glycol, dipropylene glycol, butylene glycol, 1,6-hexanediol, 1,2-hexanediol, 1,5 -Pentanediol, 1,2-pentanediol, 2,2-dimethyl-1,3-propanediol, 2-methyl-2,4-pentanediol, 3-methyl-1,5-penta Polyhydric alcohols such as diol, 3-methyl-1,3-butanediol, 2-methylpentane-2,4-diol, 2-methyl-1,3-propanediol; ethanolamine, 2- (dimethylamino) Amines such as ethanol; monohydric alcohols such as methanol, ethanol and butanol; 2,2′-thiodiethanol; sulfolanes; amides such as N, N-dimethylformamide; 2-pyrrolidone, γ-butyrolactone, propylene carbonate, carbonic acid Heterocycles such as ethylene; acetonitrile and the like are included. These may be used alone or in combination.

Among these, the solvent preferably contains an organic solvent having a boiling point of 150 ° C. or higher from the viewpoint of preventing the ink from drying near the ink jet head and improving the dischargeability from the head. Preferable examples of such an organic solvent include glycerin, propylene glycol, triethylene glycol monomethyl ether and the like.

1-5. Other Components The glittering inkjet ink may further contain other components other than the above components as long as the effects of the present invention are not impaired. Examples of other components include known surfactants (surface conditioning agents).

Examples of surfactants include anionic surfactants such as dialkyl sulfosuccinates, alkyl naphthalene sulfonates and fatty acid salts, polyoxyethylene alkyl ethers, polyoxyethylene alkyl allyl ethers, acetylene glycols and polyoxyethylenes. Nonionic surfactants such as ethylene / polyoxypropylene block copolymers, cationic surfactants such as alkylamine salts and quaternary ammonium salts, and silicone-based and fluorine-based surfactants are included.

Examples of commercially available silicone surfactants include KF-351A, KF-352A, KF-642 and X-22-4272, manufactured by Shin-Etsu Chemical, BYK-307, BYK-345, BYK-347 and BYK. -348, manufactured by Big Chemie ("BYK" is a registered trademark of the same company), TSF4452, and manufactured by Toshiba Silicone.

The content of the surfactant can be, for example, 0.001% by mass or more and less than 1.0% by mass with respect to the total mass of the ink.

1-6. Physical Properties The viscosity of the glittering ink-jet ink of the present invention is preferably 1 cP or more and less than 100 cP, and preferably 1 cP or more and 50 cP or less from the viewpoint of further improving the ejection stability from the nozzle in the image formation by the ink jet method. More preferably, it is 1 cP or more and 15 cP or less.

2. Image Forming Method Using Glitter Inkjet Ink The image forming method of the present invention includes 1) a step of volatilizing a solvent after applying the glittering inkjet ink of the present invention on a substrate (ink applying / drying step), and 2) heating the resulting glittering ink-jet ink to form a metallic gloss layer (heating step).

2-1. Ink application / drying process After the above-described glittering inkjet ink is applied onto the substrate, the solvent is volatilized.

The ink can be applied by an ink jet method. Specifically, ink is ejected from the nozzles of the inkjet head and landed on the surface of the substrate.

The method for volatilizing the solvent is not particularly limited, and may be a vacuum degassing method, an air drying method, a heat drying method, or the like. The drying temperature is preferably less than the glass transition temperature of the emulsion resin particles, for example, preferably from room temperature to less than 100 ° C, and more preferably from room temperature to less than 80 ° C.

2-2. Heating process The ink applied on the substrate is heated to form a metallic luster layer. Specifically, the emulsion resin particles in the ink applied on the substrate are thermally fused to form a metallic gloss layer.

The heating temperature of the ink may be any temperature at which the emulsion resin particles can be thermally fused, and is preferably equal to or higher than the glass transition temperature of the emulsion resin particles. Specifically, the heating temperature is preferably 40 ° C. or higher, for example, and the upper limit temperature needs to be equal to or lower than the heat resistance temperature of the base material and the emulsion resin particles. Further, it is possible to form a film at a Tg or less of the emulsion resin particles by further adding a film forming aid to the ink.

The solvent volatilization (drying) step 1) and the heating step 2) may be performed in separate steps or simultaneously. When the volatilization (drying) of the solvent of 1) and the heating of 2) are simultaneously performed, it is preferable that the drying temperature and heating temperature be equal to or higher than the glass transition temperature of the emulsion resin particles.

2-3. Formation of Other Layers The image forming method of the present invention may further include a step of forming a primer layer on the surface of the substrate before the metallic gloss layer is formed, if necessary. The image forming method of the present invention may further include a step of forming a color material layer or a protective layer on the surface layer side of the obtained metallic gloss layer.

2-3-1. Step of forming primer layer The primer layer can be formed by applying a resin composition containing a binder resin to the surface of the base material before the metallic luster layer is formed. After the application of the resin composition, the resin composition may be dried by heating or the like to form a binder resin. The drying temperature at this time can be, for example, less than 100 ° C.

The binder resin may be any resin that has been conventionally used to enhance the adhesion of a pigment containing metal nanoparticles or the like to the base material. Examples of such binder resins include (meth) acrylic resins, epoxy resins, polysiloxane resins, maleic acid resins, polyolefin resins, vinyl resins, polyamide resins, polyvinyl pyrrolidone, polyhydroxystyrene, polyvinyl alcohol, nitrocellulose, acetic acid. Examples include cellulose, ethyl cellulose, ethylene-vinyl acetate copolymer, urethane resin, polyester resin, and alkyd resin. These resins may be used alone or in combination of two or more.

2-3-2. Step of forming color material layer or protective layer The color material layer can be formed by applying a resin composition containing a known pigment or dye and a binder resin for fixing them onto the metallic luster layer. . The protective layer can be formed by applying a resin composition containing a binder resin on the metallic luster layer. After application of these resin compositions, the resin composition may be dried by heating or the like to form a binder resin. The drying temperature at this time can be, for example, less than 100 ° C.

The resin contained in each resin composition can be selected from the same resins as the binder resin contained in the primer layer.

The method for applying each resin composition is not particularly limited, but an inkjet method and an electrophotographic method are preferable from the viewpoint of easily forming a fine image.

Hereinafter, the present invention will be specifically described by way of examples, but the present invention is not limited thereto.

1. Material 1-1-1. Preparation of silver nanoparticle dispersion <silver nanoparticle dispersion 1>
To a 1 L separable flask having a flat stirring blade and a baffle plate, 7.2 g of DISPERBYK-190 (manufactured by Big Chemie, acid value of 10 mgKOH / g) as a dispersant and 252 g of ion-exchanged water were added. Stirring was performed to dissolve DISPERBYK-190. Subsequently, 62 g of silver nitrate (manufactured by Toyo Chemical Co., Ltd.) dissolved in 252 g of ion-exchanged water was charged into the separable flask with stirring. Thereafter, the separable flask was placed in a water bath and heated and stirred until the temperature of the solution was stabilized at 70 ° C. Then, using a syringe pump, 157 g of dimethylaminoethanol (manufactured by Wako Pure Chemical Industries, Ltd.) as a reducing agent was added dropwise to the separable flask over 48 minutes, and the stirring was continued for 1 hour while maintaining the temperature at 70 ° C. A reaction solution containing nanoparticles was obtained.

The obtained reaction liquid was put into a stainless steel cup, and 2 L of ion exchange water was further added, and then the pump was operated to perform ultrafiltration. After the solution in the stainless steel cup decreased, ion-exchanged water was added again, and purification was repeated until the filtrate had a conductivity of 100 μS / cm. Thereafter, the filtrate was concentrated to obtain a silver nanoparticle dispersion 1 having a solid content of 30 wt%.
The ultrafiltration device used was an ultrafiltration module AHP1010 (manufactured by Asahi Kasei Corporation, molecular weight cut off: 50000, number of membranes used: 400), and a tube pump (manufactured by Masterflex) connected by a Tygon tube. . It was 55 nm when the average particle diameter D1 of the silver nanoparticle in the obtained silver nanoparticle dispersion liquid 1 was measured.

<Silver nanoparticle dispersion 2>
In the preparation of the silver nanoparticle dispersion 1, a silver nanoparticle dispersion 2 was obtained in the same manner except that the addition amount of silver nitrate was 65 g, the dispersant was 6.8 g, and the dropping time of dimethylaminoethanol was changed to 50 minutes. . It was 105 nm when the average particle diameter D1 of the silver nanoparticle in the obtained silver nanoparticle dispersion liquid 2 was measured.

<Silver nanoparticle dispersion 3>
In the preparation of the silver nanoparticle dispersion 1, the silver nanoparticle dispersion 3 was obtained in the same manner except that the addition amount of silver nitrate was 58 g, the dispersant was 7.5 g, and the dropping time of dimethylaminoethanol was changed to 45 minutes. . It was 35 nm when the average particle diameter D1 of the silver nanoparticle in the obtained silver nanoparticle dispersion liquid 3 was measured.

<Silver nanoparticle dispersion 4>
In the preparation of the silver nanoparticle dispersion 1, a silver nanoparticle dispersion 4 was obtained in the same manner except that the addition amount of silver nitrate was 55 g, the dispersant was 8.0 g, and the dropping time of dimethylaminoethanol was changed to 45 minutes. . It was 20 nm when the average particle diameter D1 of the silver nanoparticle in the obtained silver nanoparticle dispersion liquid 4 was measured.

<Silver nanoparticle dispersion 5>
In the preparation of the silver nanoparticle dispersion 1, the silver nanoparticle dispersion 5 was obtained in the same manner except that the addition amount of silver nitrate was 65 g, the dispersant was 6.5 g, and the dropping time of dimethylaminoethanol was changed to 50 minutes. . It was 150 nm when the average particle diameter D1 of the silver nanoparticle in the obtained silver nanoparticle dispersion liquid 5 was measured.

<Silver nanoparticle dispersion 6>
In the preparation of silver nanoparticle dispersion 1, silver nanoparticle dispersion 6 was obtained in the same manner except that the amount of silver nitrate added was 69 g, the dispersant was 6.4 g, and the dimethylaminoethanol dropping time was changed to 55 minutes. . It was 200 nm when the average particle diameter D1 of the silver nanoparticle in the obtained silver nanoparticle dispersion liquid 6 was measured.

1-1-2. Preparation of gold nanoparticle dispersion <Gold nanoparticle dispersion 1>
A 1 L separable flask having a flat stirring blade and a baffle plate was charged with 3.7 g of DISPERBYK-191 (manufactured by BYK Chemie, acid value of 30 mg KOH / g) and 168 g of ethanol as a dispersant. The DISPERBYK-191 was dissolved with stirring. Subsequently, 21 g of chloroauric acid dissolved in 168 g of ethanol was added to the above separable flask while stirring. Thereafter, the separable flask was placed in a water bath and heated and stirred until the temperature of the solution was stabilized at 50 ° C. Thereafter, 19.5 g of dimethylaminoethanol (manufactured by Wako Pure Chemical Industries, Ltd.) as a reducing agent was added, and stirring was continued for 2 hours while maintaining the temperature at 50 ° C. to obtain a reaction solution containing gold nanoparticles.

The obtained reaction liquid was put into a stainless steel cup, 2 L of ethanol was further added, and then the pump was operated to perform ultrafiltration. After the solution in the stainless steel cup decreased, ion-exchanged water was added, and purification was repeated until the filtrate had a conductivity of 30 μS / cm. Thereafter, the filtrate was concentrated to obtain a gold nanoparticle dispersion 1 having a solid content of 30 wt%.
The ultrafiltration device used was an ultrafiltration module AHP1010 (manufactured by Asahi Kasei Corporation, molecular weight cut off: 50000, number of membranes used: 400), and a tube pump (manufactured by Masterflex) connected by a Tygon tube. . It was 30 nm when the average particle diameter D1 of the gold nanoparticle in the obtained gold nanoparticle dispersion liquid 1 was measured.

1-2. Preparation of emulsion resin particle dispersion <Emulsion resin particle dispersion 1>
In a 200 ml four-necked flask equipped with a stirrer, thermometer, cooling pipe, and nitrogen gas introduction pipe, 19 g of sodium sulfonate-containing polyester polyol as the sulfonate-containing polyol (a1), organic polyisocyanate (a2) 8 g of isophorone diisocyanate was added and reacted at 80 ° C. for 2 hours. Thereafter, 0.8 g of 1,4-butanediol as a low molecular polyol (a3-1) and 5 g of propylene glycol dimethyl ether (DMPDG) as an aqueous solvent were added and reacted at 80 ° C. for 2 hours. Thereafter, 60 g of water as an aqueous solvent and 5 g of propylene glycol dimethyl ether were added and emulsified, and an aqueous amine solution in which 0.5 g of ethylenediamine as a low molecular weight polyamine (a3-2) was dissolved in 15 g of water was reacted at 50 ° C. for 3 hours. The resulting emulsion was diluted with water to a solid content concentration of 20% to obtain an emulsion resin particle dispersion 1 (urethane emulsion solution). It was 40 nm when the average particle diameter D2 of the emulsion resin particle in the obtained emulsion resin particle dispersion 1 was measured.

<Emulsion resin particle dispersion 2>
19 g of sodium sulfonate-containing polyester polyol and 8 g of isophorone diisocyanate were charged in a 200 ml four-necked flask equipped with a stirrer, a thermometer, a cooling tube, and a nitrogen gas introduction tube, and reacted at 80 ° C. for 2 hours. Thereafter, 0.9 g of 1,4-butanediol and 7 g of propylene glycol dimethyl ether were added and reacted at 80 ° C. for 2 hours. Thereafter, 60 g of water and 7 g of propylene glycol dimethyl ether were added to emulsify, and an aqueous amine solution in which 0.5 g of ethylenediamine was dissolved in 15 g of water was reacted at 50 ° C. for 4 hours, and the resulting emulsion had a solid content concentration of 20%. The emulsion resin particle dispersion 2 (urethane emulsion solution) was obtained. It was 80 nm when the average particle diameter D2 of the emulsion resin particle in the obtained emulsion resin particle dispersion 2 was measured.

<Emulsion resin particle dispersion 3>
19 g of sodium sulfonate-containing polyester polyol and 8 g of isophorone diisocyanate were charged in a 200 ml four-necked flask equipped with a stirrer, a thermometer, a cooling tube, and a nitrogen gas introduction tube, and reacted at 80 ° C. for 2 hours. Thereafter, 0.9 g of 1,4-butanediol and 5 g of propylene glycol dimethyl ether were added and reacted at 80 ° C. for 2 hours. Thereafter, 60 g of water and 5 g of propylene glycol dimethyl ether were added and emulsified, and an aqueous amine solution in which 0.5 g of ethylenediamine was dissolved in 15 g of water was reacted at 50 ° C. for 4 hours, and the resulting emulsion had a solid content concentration of 20%. The emulsion resin particle dispersion 3 (urethane emulsion solution) was obtained. It was 20 nm when the average particle diameter D2 of the emulsion resin particle in the obtained emulsion resin particle dispersion 3 was measured.

<Emulsion resin particle dispersion 4>
A four-necked flask equipped with a stirrer, a thermometer, a cooling tube, and a nitrogen gas introduction tube was charged with 140 g of isopropyl alcohol as a solvent, heated to 85 ° C., and then introduced with 12.5 g of methacrylic acid while introducing nitrogen gas. Then, a mixture of 60.5 g of methyl methacrylate and 23 g of 2-ethylhexyl acrylate and 4 g of a reaction initiator (“ABN-E” manufactured by Nippon Hydrazine Kogyo Co., Ltd.) was added dropwise over 2 hours. After the dropwise addition, the same temperature was further maintained for polymerization for 2 hours, and then the solvent was distilled off under reduced pressure to obtain a water-soluble resin having a glass transition temperature of 50 ° C.
Next, after 96 g of the obtained water-soluble resin was pulverized, it was added to 140 g of water in which ammonia equivalent to the carboxyl group contained in the water-soluble resin calculated from the monomer composition was dissolved, stirred and mixed, and heated at 80 ° C. It was dissolved to obtain an aqueous solution (A) of a polymer emulsifier having a solid content concentration of 40%.
A four-necked flask equipped with a stirrer, a thermometer, a cooling tube, and a nitrogen gas introduction tube was charged with 240 g of an aqueous solution of polymer emulsifier (A) and 90 g of water, and maintained at 80 to 85 ° C. while introducing nitrogen gas, 86 g of methyl methacrylate, 58 g of 2-ethylhexyl acrylate, and 60 g of 1% ammonium persulfate aqueous solution were added dropwise from another dropping port over 2 hours. After the dropwise addition, the emulsion is subjected to emulsion polymerization for 2.5 hours while maintaining the same temperature. The obtained emulsion is diluted with water so that the solid content concentration becomes 20%, and emulsion resin particle dispersion 4 (acrylic emulsion solution) is obtained. Obtained. It was 45 nm when the average particle diameter D2 of the emulsion resin particle in the obtained emulsion resin particle dispersion 4 was measured.

<Emulsion resin particle dispersion 5>
In a four-necked flask equipped with a stirrer, thermometer, cooling tube, and nitrogen gas introduction tube, 220 g of ion-exchanged water and 1.8 g of an emulsifier (Daiichi Kogyo Seiyaku Co., Ltd. “Hytenol 18E”) were ion-exchanged. The total amount of the emulsifier aqueous solution dissolved in 8 g was charged and heated to 72 ° C. while introducing nitrogen gas, and then 2.8 g of methacrylic acid, 13 g of methyl methacrylate, 1.9 g of 2-ethylhexyl acrylate and thioglycolic acid 2 -1 g of ethylhexyl and 13 g of 5% ammonium persulfate aqueous solution were added, and after 15 minutes, 11.2 g of methacrylic acid, 53 g of methyl methacrylate, 7.6 g of 2-ethylhexyl acrylate, and 4 g of 2-ethylhexyl thioglycolate were added over 80 minutes. And dripped. After 15 minutes from the end of dropping, the mixture was heated to 75 ° C., and 25% aqueous ammonia was added to obtain an aqueous solution (C) of a polymer emulsifier.
Further, the aqueous solution (C) of this polymer emulsifier was adjusted to 80 ° C., and 86 g of methyl methacrylate, 58 g of 2-ethylhexyl acrylate and 100 g of ion-exchanged water were added dropwise over 90 minutes. Thereafter, 7.2 g of a 2% ammonium persulfate aqueous solution was added dropwise over 30 minutes. Aging was performed while maintaining the temperature for 90 minutes, and the resulting emulsion was diluted with water to a solid content concentration of 20% to obtain an emulsion resin particle dispersion 5 (acrylic emulsion solution). It was 15 nm when the average particle diameter D2 of the emulsion resin particle in the obtained emulsion resin particle dispersion 5 was measured.

<Emulsion resin particle dispersion 6>
A four-necked flask equipped with a stirrer, a thermometer, a cooling tube, and a nitrogen gas introduction tube was charged with 140 g of isopropyl alcohol as a solvent, heated to 85 ° C., and then introduced with 3.2 g of methacrylic acid while introducing nitrogen gas, A mixture of 48 g of methyl methacrylate, 12 g of 2-ethylhexyl acrylate, 33 g of styrene, and 4 g of a reaction initiator (“ABN-E” manufactured by Nippon Hydrazine Industry Co., Ltd.) was added dropwise over 2 hours. After the dropwise addition, the same temperature was further maintained for polymerization for 2 hours, and then the solvent was distilled off under reduced pressure to obtain a water-soluble resin having a glass transition temperature of 70 ° C.
Next, after 96 g of the obtained water-soluble resin was pulverized, it was added to 140 g of water in which ammonia equivalent to the carboxyl group contained in the water-soluble resin calculated from the monomer composition was dissolved, stirred and mixed, and heated at 80 ° C. By dissolving, an aqueous solution (B) of a polymer emulsifier having a solid concentration of 40% was obtained.
A four-necked flask equipped with a stirrer, a thermometer, a cooling tube, and a nitrogen gas introduction tube was charged with 240 g of an aqueous solution of polymer emulsifier (B) and 90 g of water, and maintained at 80 to 85 ° C. while introducing nitrogen gas, 86 g of methyl methacrylate, 58 g of 2-ethylhexyl acrylate, and 60 g of 1% ammonium persulfate aqueous solution were added dropwise from another dropping port over 2 hours. After the dropwise addition, the same temperature was further maintained for 3 hours to carry out emulsion polymerization, and the obtained emulsion was diluted with water so that the solid content concentration was 20% to obtain an emulsion resin particle dispersion 6 (acrylic emulsion solution). . It was 120 nm when the average particle diameter D2 of the emulsion resin particle in the obtained emulsion resin particle dispersion 6 was measured.

<Emulsion resin particle dispersion 7>
In a four-necked flask equipped with a stirrer, thermometer, cooling tube, and nitrogen gas introduction tube, 220 g of ion-exchanged water and 1.8 g of an emulsifier (Daiichi Kogyo Seiyaku Co., Ltd. “Hytenol 18E”) were ion-exchanged. The total amount of the emulsifier aqueous solution dissolved in 8 g was charged and heated to 72 ° C. while introducing nitrogen gas, and then 2.8 g of methacrylic acid, 13 g of methyl methacrylate, 1.9 g of 2-ethylhexyl acrylate and thioglycolic acid 2 -1 g of ethylhexyl and 10 g of 5% ammonium persulfate aqueous solution were added, and after 10 minutes, 11.2 g of methacrylic acid, 53 g of methyl methacrylate, 7.6 g of 2-ethylhexyl acrylate and 4 g of 2-ethylhexyl thioglycolate were applied over 60 minutes. And dripped. 15 minutes after the completion of the dropping, the mixture was heated to 70 ° C., and 25% aqueous ammonia was added. The temperature was further adjusted to 75 ° C., and 86 g of methyl methacrylate, 58 g of 2-ethylhexyl acrylate and 100 g of ion-exchanged water were added dropwise over 90 minutes. Thereafter, 6 g of a 2% ammonium persulfate aqueous solution was dropped over 30 minutes. Aging was carried out while maintaining the temperature for 60 minutes, and the obtained emulsion was diluted with water so as to have a solid content concentration of 20% to obtain an emulsion resin particle dispersion 7 (acrylic emulsion solution). It was 6 nm when the average particle diameter D2 of the emulsion resin particle in the obtained emulsion resin particle dispersion liquid 7 was measured.

Average particle diameter D1 of silver nanoparticles in the obtained silver nanoparticle dispersions 1-6, average particle diameter D1 of gold nanoparticles in gold nanoparticle dispersion 1, and emulsion resin particles in emulsion resin particle dispersions 1-7 The average particle diameter D2 was measured by the following methods.

<Measurement of average particle diameter>
The average particle diameter D1 of the metal nanoparticles and the average particle diameter D2 of the emulsion resin particles were measured by SEM observation. Specifically, it measured by the following procedures.
1) After applying the dispersion on a glass plate, vacuum degassing was performed to volatilize the solvent component to obtain a sample. The obtained sample dispersion was subjected to SEM observation using a measuring device JEOL JSM-7401F, and the particle diameters of arbitrary 300 metal nanoparticles or emulsion resin particles were measured.
2) Based on the obtained measurement data, volume-based particle size distribution was obtained using image processing software Image J, and D50 (median diameter) was defined as the average particle diameter (volume average particle diameter).
In addition, in SEM observation, since the dispersing agent adsorbed on the surface of the metal nano cannot be observed, the particle size of the metal nano was determined as the particle size of the metal nano not including the dispersant.

1-3. Solvent Water Propylene glycol (boiling point: 188 ° C)
Triethylene glycol monomethyl ether (boiling point: 248 ° C)

1-4. Additive BYK-348 (by Big Chemie) (Surfactant)

2. Preparation of Ink According to the composition described in Table 1 or 2, each component was mixed and then filtered through a 3 μm membrane filter manufactured by ADVATEC (“Teflon” is a registered trademark of DuPont). Examples 1 to 20 and Comparative Examples 1 to 5 inks were prepared.

3. Ink Evaluation Images were formed on the following substrates using the inks of Examples 1 to 20 and Comparative Examples 1 to 5.

(Base material)
Coated paper: Ramie Corporation, WRG3-36

(Image formation conditions)
Images were formed on each substrate using an ink jet recording apparatus having a piezo ink jet nozzle. The ink jet recording apparatus has an ink tank, an ink supply pipe, an ink supply tank immediately before the ink jet head, a filter, and a piezo type ink jet head in this order from the upstream side to the downstream side where the ink flows. . The ink-jet head was driven under the conditions of a droplet amount of 14 pl, a printing speed of 0.5 m / sec, an ejection frequency of 10.5 kHz, and a printing rate of 100%, and ink droplets were ejected and landed on each substrate. . After landing, the film was dried at 60 ° C. for about 10 minutes to obtain an image.

Then, the reflectance and adhesion of the obtained image and the ejection stability of the ink were evaluated by the following methods, respectively.

(Reflectance)
Using a spectrophotometer U4100, the reflectance at each wavelength of 450 nm, 550 nm, and 650 nm was measured, and an average value thereof was obtained and evaluated according to the following criteria.
A: The average value is 50% or more O: The average value is less than 50% 40% or more Δ: The average value is less than 40% 30% or more X: The average value is less than 30% 20% or more XX: The average The value was less than 20%.
However, about Example 20, the reflectance in each wavelength of 600 nm and 650 nm was measured, and it evaluated by those average values.

(Adhesion)
On the surface of the obtained image, cuts were made in a grid pattern so that the number of grids was 100, and a grid tape peeling test was performed. And it evaluated by the following reference | standard.
○: No peeling at 100/100 grids Δ: No peeling at 99/100 to 95/100 grids ×: No peeling at 94 / 100-0 / 100 grids △ or more Was evaluated as practical.

(Discharge stability)
The ink supply tank of the inkjet image forming apparatus is filled with the obtained ink, and at room temperature, the droplet amount is 42 pl, the printing speed is 0.5 m / sec, the ejection frequency is 10.5 kHz, and the printing rate is 100%. Ink droplets were ejected continuously for 8 hours to land on the substrate.
During 8 hours of continuous discharge, visually observe the number of occurrences of missing dots, flying bends and ink splashes on the substrate, and evaluate the discharge stability of the ink composition based on the total number of times based on the following criteria: did.
○ The number of missing dots, flying bends and ink splashes is less than 15 △ The number of missing dots, flying bends and ink splashes is 15 or more and less than 20 times × The number of missing dots, flying bends and ink splashes is 20 More than △ times or more was evaluated as practical.

The obtained evaluation results are shown in Tables 1 and 2.

As shown in Table 1, the images obtained using the inks of Examples 1 to 20 having D2 / D1 of more than 0.05 and less than 1 all have high reflectivity and also have good adhesion to the substrate. It turns out that it is favorable.

In particular, it can be seen that by setting M1 / M2 to 1.3 or more and 35 or less, the reflectance of the obtained image is higher and the adhesion to the substrate can be further improved (the inks of Examples 3 and 8 to 11). Comparison with the inks of Examples 16 to 17). Furthermore, it can be seen that by setting M1 / M2 to 2 or more, the reflectance of the obtained image can be further increased (contrast of ink of Example 8 and ink of Example 16).

It can also be seen that by setting M1 + M2 to 1 or more, the reflectance of the obtained image can be made higher, and by setting it to 35 or less, ejection stability can be easily obtained (inks of Examples 3 and 10 to 11). And the inks of Examples 18 to 19). The reason why the reflectivity is increased by setting M1 + M2 to 1 or more is considered to be that a sufficient film thickness is easily obtained to increase the reflectivity because the solid concentration is appropriately high. The reason why the ejection stability is increased by setting M1 + M2 to 35 or less is considered that the solid content concentration is not too high and the increase in ink viscosity is small.

In contrast, it can be seen that the image obtained using the ink of Comparative Example 1 containing no emulsion resin particles has low adhesion to the substrate. On the other hand, it can be seen that the images obtained using the inks of Comparative Examples 2 to 4 containing emulsion resin particles but having D2 / D1 of 1 or more have low reflectance and adhesion to the substrate. In particular, in comparison with Comparative Examples 2 and 3, if the average particle diameter D2 of the emulsion resin particles is relatively large, a large number of voids around the metal nanoparticles are formed when the content of the emulsion resin particles is reduced. Therefore, the refractive index extinction coefficient of the obtained metallic luster layer is increased, and the scattering factor is increased, indicating that the reflectance and adhesion are further decreased. Further, it can be seen that an image obtained using the ink of Comparative Example 5 containing emulsion resin particles but having D2 / D1 of less than 0.05 has particularly low adhesion to the substrate. This is presumably because the average particle diameter D2 of the emulsion resin particles is relatively small, and the binding between the resin particles is insufficient, and sufficient film strength cannot be obtained.

This application claims priority based on Japanese Patent Application No. 2017-065900 filed on Mar. 29, 2017. All the contents described in the application specification are incorporated herein by reference.

ADVANTAGE OF THE INVENTION According to this invention, the inkjet ink which can form the image which has sufficient adhesiveness with a base material and has sufficient metal luster can be provided.

Claims (9)

1. Metal nanoparticles, a dispersant adsorbed on the surface of the metal nanoparticles, emulsion resin particles, and a solvent,
   A glittering inkjet ink satisfying 0.05 <D2 / D1 <1, where D1 is an average particle diameter of the metal nanoparticles and D2 is an average particle diameter of the emulsion resin particles.
2. 2. The glitter according to claim 1, further satisfying 1.3 ≦ M1 / M2 ≦ 35, where M1 (%) is the mass of the metal nanoparticles and M2 (%) is the mass of the emulsion resin particles. Inkjet ink.
3. The glittering inkjet ink according to claim 1 or 2, further satisfying 1≤M1 + M2≤35, where M1 (%) is the content of the metal nanoparticles and M2 (%) is the content of the emulsion resin particles. .
4. The glitter inkjet ink according to any one of claims 1 to 3, wherein the dispersant is a polymer dispersant.
5. The glittering ink jet according to claim 4, wherein the polymer dispersant is a comb block copolymer in which a main chain includes a structural unit derived from a (meth) acrylic acid ester and a side chain includes a polyoxyalkyl group. ink.
6. The glitter inkjet ink according to any one of claims 1 to 5, wherein the emulsion resin particles are urethane resin particles or (meth) acrylic resin particles.
7. The glitter ink jet ink according to any one of claims 1 to 6, wherein the solvent contains an organic solvent having a boiling point of 150 ° C or higher.
8. The glittering inkjet ink according to any one of claims 1 to 7, wherein the metal nanoparticles are silver nanoparticles.
9. A step of volatilizing the solvent after applying the glittering inkjet ink according to any one of claims 1 to 8 on a substrate;
   Heating the glitter inkjet ink from which the solvent is volatilized to form a metallic gloss layer.